Nanoparticle structures and composite materials comprising a silicon-containing compound having a chemical linker that forms a non-covalent bond with a polymer

ABSTRACT

Nanoparticle precursor structures, nanoparticle structures, and composite materials that include the nanoparticle structures in a polymer to form a composite material. The nanoparticle structures have chemical linkage moieties capable of forming non-covalent bonds with portions of a polymer for the composite material. Such composite materials are useful as biomaterials in medical devices.

FIELD OF THE DISCLOSURE

The present disclosure relates to composite materials containingnanoparticles having chemical linkage moieties capable of formingnon-covalent bonds with portions of a polymer. Such composite materialsare useful as biomaterials in medical devices.

BACKGROUND OF THE DISCLOSURE

Biomaterials research involves many areas of material science. The areaof material science generally depends on the intended application of thebiomaterial. For example, metals and metal alloys are used inorthopedics, dentistry and other load bearing applications; ceramics areused because of their chemically inert nature or their high bioactivity;polymers are used for soft tissue replacement and used for many othernon-structural applications.

Regardless of their application, biomaterials are often required tomaintain a balance between application specific mechanical propertiesand their biological effect on the body. So, biomaterial are oftenrequired to display a range of properties, such as biological activity(or inactivity), mechanical strength, chemical durability, etc. Theseaspects of biomaterial design are important to the successfulapplication of the biomaterial to a given situation and/or application.Use of composite technology has enabled biomedical material researchersto develop a wide range of new biocomposites, which offer the promise toimprove the quality of life of many people.

In a specific example, attempts have been made to incorporate ceramicand/or metallic nanoparticles into polymer matrices for the purpose ofimproving both the durability and surface characteristics (e.g.,abrasion resistance) of polymers. However, the ceramic and/or metallicnanoparticles tend to conglomerate or clump when processed or mixed intothe base polymer material. A suitable solution to this problem isdesired.

DETAILED DESCRIPTION OF DISCLOSURE

The present disclosure provides nanoparticle precursor structures,nanoparticle structures and composite materials that include thenanoparticle structures in a polymer, where the composite materials canbe suitable for use in medical devices. Composite materials having thepolymer and nanoparticle structure of the present disclosure displaysexcellent performance in many characteristics important for medicaldevice use, including compressive strength, diametral tensile strength,flexural strength, fracture toughness, puncture resistance, hardness,resistance to wear (e.g., characterized by compressive strength anddiametral tensile strength), durability, thermal expansion, visualopacity, x-ray opacity, impact strength, chemical durability, electricalconductivity, biocompatibility, modulus, shelf life, patient comfort,ease-of-use, and structural integrity relative to a polymer without thenanoparticle structures of the present disclosure.

The addition of the nanoparticle structures to the polymer providesdesirable levels of viscosity for composite material processing andstrength for durability of the finished product relative to a polymerwithout the nanoparticle structures of the present disclosure. Thenanoparticle structure of the present disclosure can also be used as abulk material and/or a coating with or without the polymer.

As used herein, a “composite material” refers to a polymer thatcontains, at least in part, nanoparticle structures of the presentdisclosure, and any desired filler and/or adjuvants. The polymer and thenanoparticle structures each include chemical linkage moieties capableof forming non-covalent bonds that allow the components of the compositematerial to be dispersed, as discussed herein. Composite materials ofthe present disclosure can be multiple- or one-part compositions, aswill be discussed herein.

As used herein, “dispersed” may be defined as a process or techniqueused to mix the nanoparticle structures of the present disclosure evenlythroughout a polymer to form a mixture. As used herein a “mixture” canbe defined as the state formed by two or more ingredients that do notbear a fixed proportion to one another and that, however commingled, areconceived as retaining a separate existence. As used herein, to “mix”can be defined as a process, operation or technique used to distributethe nanoparticle precursor and/or nanoparticle structures of the presentdisclosure evenly throughout a polymer. In other words, mixing reducesthe nonuniformity of the mixture. Examples of such processes and/ortechniques include, but are not limited to, mixing operations thatreduce composition nonuniformity of the nanoparticle precursorstructures and/or nanoparticle structures and the polymer. While themixing process can result in production of a homogeneous product, asomewhat heterogeneous product is within the scope of this disclosure.

Examples of suitable mixing processes include, but are not limited to,the use of a batch mixer, a continuous mixer, a motionless mixer, and ascrew extruder (single or twin barrel), among others. Surprisingly, thenanoparticle structures of the present disclosure can undergo melting,either alone or with the polymer, without significant thermaldegradation.

The resulting nanoparticle structures are dispersed throughout thepolymer to provide both mechanical and surface properties to theresulting composite material imparted through both the nanoparticlestructure and the interactions of the nanoparticle structure with thepolymer. In one embodiment, the nanoparticle structures can be dispersedby mixing the nanoparticles into a melt (i.e., a liquid state) of thepolymer.

In addition, the composite material of the present disclosure can befurther characterized in that it can be substantially insoluble in bodyfluids and tissues and that is designed and constructed to be placed inor onto the body or to contact fluid or tissue of the body. Ideally, thecomposite material will be biostable, biocompatible, and will not inducereactions in the body such as blood clotting, tissue death, tumorformation, allergic reaction, foreign body reaction (rejection) orinflammatory reaction; will have the physical properties such asstrength, elasticity, permeability and flexibility required to functionfor the intended purpose; can be purified, fabricated and sterilized;and will substantially maintain its physical properties and functionduring the time that it remains implanted in or in contact with thebody. A “biostable” material is one that is not broken down by the body,whereas a “biocompatible” material is one that is not rejected by thebody.

As used herein, a “medical device” may be defined as a device that hassurfaces that contact blood or other body fluids and/or tissues in thecourse of their operation. This can include, for example, extracorporealdevices for use in surgery such as blood oxygenators, blood pumps, bloodsensors, tubing used to carry blood and the like which contact bloodwhich is then returned to the patient. This can also include implantabledevices such as vascular grafts, stents, electrical stimulation leads,valves for use in the cardiac system (e.g., heart valves), orthopedicdevices, catheters, catheter shaft components, filters, guide wires,shunts, sensors, membranes, balloons, replacement devices for nucleuspulposus, cochlear or middle ear implants, intraocular lenses, coatingsfor such devices, and the like.

Nanoparticle structures and the composite material of the presentdisclosure can be used in medical devices as well as nonmedical devices.As discussed, they can be used in medical devices and are suitable asbiomaterials. Examples of medical devices are listed herein. Examples ofnonmedical devices include foams, insulation, clothing, footwear,paints, coatings, adhesives, and building construction materials,besides others.

As used herein, chemical linkage moieties capable of forming a“non-covalent bond” include those linkages that are capable of forming achemical bond in that allow for non-bonded interactions due to van derWaals, electrostatic, and/or hydrogen bonding forces. For example,chemical linkage moieties capable of forming a “non-covalent bond”include those that can form hydrogen bonds such as, but not limited to,urethane linkages, amide linkages, ester linkages, and combinationthereof.

As used herein, the term “organic group” is used for the purpose of thisdisclosure to mean a hydrocarbon group that is classified as analiphatic group, cyclic group, or combination of aliphatic and cyclicgroups (e.g., alkaryl and aralkyl groups). In the context of the presentdisclosure, suitable organic groups for polymeric hybrid precursors ofthis disclosure are those that do not interfere with the formation ofthe nanoparticle structure.

In the context of the present disclosure, the term “aliphatic group”means a saturated or unsaturated linear or branched hydrocarbon group.This term is used to encompass alkyl (e.g., —CH₃, which is considered a“monovalent” group) (or alkylene if within a chain such as —CH₂—, whichis considered a “divalent” group), alkenyl (or alkenylene if within achain), and alkynyl (or alkynylene if within a chain) groups, forexample. The term “alkyl group” means a saturated linear (i.e., straightchain), cyclic (i.e., cycloaliphatic), or branched monovalenthydrocarbon group including, for example, methyl, ethyl, n-propyl,isopropyl, t-butyl, amyl, heptyl, dodecyl, octadecyl, 2-ethylhexyl, andthe like. The term “alkenyl group” means an unsaturated, linear orbranched monovalent hydrocarbon group with one or more olefinicallyunsaturated groups (i.e., carbon-carbon double bonds), such as a vinylgroup. The term “alkynyl group” means an unsaturated, linear or branchedmonovalent hydrocarbon group with one or more carbon-carbon triplebonds. The term “cyclic group” means a closed ring hydrocarbon groupthat is classified as an alicyclic group, aromatic group, orheterocyclic group. The term “alicyclic group” means a cyclichydrocarbon group having properties resembling those of aliphaticgroups. The term “aromatic group” or “aryl group” means a mono- orpolynuclear aromatic hydrocarbon group. These hydrocarbon groups may besubstituted with heteroatoms, which can be in the form of functionalgroups. The term “heteroatom” means an element other than carbon (e.g.,fluorine, nitrogen, oxygen, sulfur, chlorine, etc.).

As a means of simplifying the discussion and the recitation of certainterminology used throughout this disclosure, the terms “group” and“moiety” are used to differentiate between chemical species that allowfor substitution or that can be substituted and those that do not soallow for substitution or can not be so substituted. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withnonperoxidic O, N, S, Si, or F atoms, for example, in the chain as wellas carbonyl groups or other conventional substituents. Where the term“moiety” is used to describe a chemical compound, linkage orsubstituent, only an unsubstituted chemical material is intended to beincluded. For example, the phrase “alkyl group” is intended to includenot only pure open chain saturated hydrocarbon alkyl substituents, suchas methyl, ethyl, propyl, t-butyl, and the like, but also alkylsubstituents bearing further substituents known in the art, such ashydroxy, alkoxy, alkylsulfonyl, halogen atoms, cyano, nitro, amino,carboxyl, etc. Thus, “alkyl group” includes ether groups, haloalkyls,nitroalkyls, carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc. On theother hand, the phrase “alkyl moiety” is limited to the inclusion ofonly pure open chain saturated hydrocarbon alkyl substituents, such asmethyl, ethyl, propyl, t-butyl, and the like.

As used herein, the terms “a,” “an,” “the,” “one or more,” and “at leastone” are used interchangeably and include plural referents unless thecontext clearly dictates otherwise. Unless defined otherwise, allscientific and technical terms are understood to have the same meaningas commonly used in the art to which they pertain. For the purpose ofthe present invention, additional specific terms are defined throughout.

The present disclosure relates to compounds of a nanoparticle precursorstructure that include at least one silicon alkoxide having a chemicallinkage moiety that can form a non-covalent bond for interaction withportions of a polymer. These compounds are of the formula (Formula I):(R₁O)_(w)Si(R₂-A-R)_(z)

where A is the chemical linkage moiety that can form a non-covalent bondwith a portion of a polymer. Each R, R₁, and R₂ can be the same ordifferent (i.e., is independently) an organic group. Examples of suchorganic groups include a straight chain or branched alkyl group, astraight chain or branched alkylene group, where each R, R₁, and R₂optionally includes heteroatoms that may be in the chain of the organicgroup or pendant therefrom as in a functional group. Each w and z can beindependently 1 to 3.

The present disclosure also relates to compounds of a nanoparticlestructure formed from the nanoparticle precursor structure of Formula Ithrough, for example, a sol-gel process with at least one siliconalkoxide of the formula (Formula II):Si(OR₃)₄

where R₃ is an organic group. Examples of the organic group includethose defined herein for each of R, R₁, and R₂. The nanoparticlestructure includes a core of a silicon-oxide based polymer with anorganic group that extends from the core, where the silicon-oxide basedpolymer of the core is formed using a sol-gel process, and the organicgroup extending from the core includes a chemical linkage moiety thatcan form a non-covalent bond.

The resulting nanoparticle structure includes a compound of the formula(Formula III):[(Si—O)_(n)—(Si—O)_(m)]_(p)—(R₂-A-R)_(r)where A is the chemical linkage moiety that can form a non-covalent bondwith a portion of the polymer. Each R and R₂ are independently anorganic group, as defined herein. The value for each of “n”, “m” and “p”is an average value in a polymeric range, with r being at least 25percent (25%) of the value of n. The silicon-oxide based polymer[(Si—O)_(n)—(Si—O)_(m)]_(p) forms a nanoparticle structure from whichthe groups (R₂-A-R)_(r) extend.

As used herein, the “polymeric range” for the values for n, m, and p areeach independently 1-100,000, 1-50,000, 1-10,000, 1-5000,1-2000, 1-1000,1-500, 1-200, 1-100, 1-50, and 1-20, that provide for a number-averagemolecular weight for [(Si—O)_(n)—(Si—O)_(m)]_(p) of 1,000,000 or more.

As used herein, a “core” of the silicon oxide based polymer includes across-linked network of silicon oxides of the formula[(Si—O)_(n)—(Si—O)_(m)]_(p) having a size in the nanometer range (e.g.,1-1000 nanometers).

In one embodiment, each R is independently a straight chain or branchedalkyl group optionally including heteroatoms, such as nitrogen, oxygen,phosphorus, sulfur, and halogen. The heteroatoms can be in the backboneof the R or pendant therefrom, and they can form functional groups. Suchheteroatom-containing groups (e.g., functional groups) include, forexample, an alcohol, carbonyl, ether, acetoxy, ester, aldehyde,acrylate, amine, amide, imine, imide, and nitrile, whether they beprotected or unprotected. In one embodiment, R does not includeheteroatoms. In an additional embodiment, each R is independently astraight chain or branched alkyl group includes 18 carbon atoms or less.In a further embodiment, each R is independently a straight chain orbranched (C2-C18) alkyl group. In other embodiments, each R isindependently a straight chain or branched (C2-C8) alkyl group (e.g.,ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, hepyl, or octyl). Inone example, R is a C4 alkyl group.

In one embodiment, each R₁ is independently a straight chain or branchedalkyl group optionally including heteroatoms, such as nitrogen, oxygen,phosphorus, sulfur, and halogen. The heteroatoms can be in the backboneof the R₁ or pendant therefrom, and they can form functional groups.Such heteroatom-containing groups (e.g., functional groups) include, forexample, an alcohol, carbonyl, ether, acetoxy, ester, aldehyde,acrylate, amine, amide, imine, imide, and nitrile, whether they beprotected or unprotected. In one embodiment, R₁ does not includeheteroatoms. In an additional embodiment, each R₁ is independently astraight chain or branched alkyl group includes 18 carbon atoms or less.In a further embodiment, each R₁ is independently a straight chain orbranched (C2-C8) alkyl group. In other embodiments, each R₁ isindependently a straight chain or branched (C2-C4) alkyl group (e.g.,ethyl, n-propyl, isopropyl, or butyl). In one example, R₁ is a C2 alkylgroup.

In one embodiment, each R₂ is independently a straight chain or branchedalkylene group optionally including heteroatoms, such as nitrogen,oxygen, phosphorus, sulfur, and halogen. The heteroatoms can be in thebackbone of R₂ or pendant therefrom, and they can form functionalgroups. Such heteroatom-containing groups (e.g., functional groups)include, for example, an alcohol, carbonyl, ether, acetoxy, ester,aldehyde, acrylate, amine, amide, imine, imide, and nitrile, whetherthey be protected or unprotected. In one embodiment, R₂ does not includeheteroatoms. In an additional embodiment, each R₂ is independently astraight chain or branched alkylene group includes 18 carbon atoms orless. In a further embodiment, each R₂ is independently a straight chainor branched (C2-C8) alkylene group. In other embodiments, each R₂ isindependently a straight chain or branched (C2-C4) alkylene group (e.g.,ethylene, n-propylene, isopropylene, or butylene). In one example, R₂ isa C3 alkylene group.

In one embodiment, each R₃ is independently a straight chain or branchedalkyl group optionally including heteroatoms, such as nitrogen, oxygen,phosphorus, sulfur, and halogen. The heteroatoms can be in the backboneof R₃ or pendant therefrom, and they can form functional groups Suchheteroatom-containing groups (e.g., functional groups) include, forexample, an alcohol, carbonyl, ether, acetoxy, ester, aldehyde,acrylate, amine, amide, imine, imide, and nitrile, whether they beprotected or unprotected. In one embodiment, R₃ does not includeheteroatoms. In an additional embodiment, each R₃ is independently astraight chain or branched alkyl group includes 18 carbon atoms or less.In a further embodiment, each R₃ is independently a straight chain orbranched (C2-C8) alkyl group. In other embodiments, each R₃ isindependently a straight chain or branched (C2-C4) alkyl group (e.g.,ethyl, n-propyl, isopropyl, or butyl). In one example, R₃ is a C2 alkylgroup.

As will be appreciated, each of R, R₁, and R₃ can be either an alkylgroup, as discussed herein, or an alkyl moiety, and R₂ can be either analkylene group, as discussed herein, or an alkylene moiety. In addition,for the formulas herein, R, R₁, R₂, and R₃ can vary within any onemolecule. For example, in addition to each R and R₂ being the same ordifferent within each [(Si—O)_(n)—(Si—O)_(m)]_(p)—(R₂-A-R)_(r) group,the R₂-A-R group can be the same or different in any one molecule.

Methods of preparation of nanoparticle precursor structures,nanoparticle structures, and composite materials that includenanoparticle structures dispersed in a polymer are also provided.Nanoparticle precursor structures of the formula (Formula I):(R₁O)_(w)Si(R₂-A-R)_(z) are capable of forming, either alone or withother precursor compounds (e.g., least one silicon alkoxide), ananoparticle structure, as discussed herein.

Although certain nanoparticle precursor structures are described herein,the nanoparticle precursor structures used to form the nanoparticlestructures of the present disclosure can be formed from a wide varietyof silicon alkoxides having chemical groups that can form chemicallinkage moieties capable of forming non-covalent bonds with portions ofthe polymer. For example, a method of preparing the nanoparticleprecursor structures involves the combining of (1) silicon alkoxideshaving chemical groups that can form chemical linkage moieties capableof forming non-covalent bonds and (2) a reactive reagent that can formthe nanoparticle precursor structure of the formula (Formula I):(R₁O)_(w)Si(R₂-A-R)_(z).

The term “reactive reagent” in the context of the present disclosure isto be understood as meaning compounds which can act as solvents ordiluents for the composition used for forming the nanoparticle precursorstructure and also contain functional chemical groups that can reactantto covalently bond to the silicon alkoxide so as to form the chemicallinkage moiety capable of forming non-covalent bonds.

Examples of nanoparticle precursor structures can be prepared from anamine-containing silicon alkoxide and the reactive reagent having the Rgroup and at least one functional group reactive with the amine group onthe silicon alkoxide, such as an acids, acyl chlorides, or amides toform an amide for the chemical linkage moiety, A in Formula I, capableof forming non-covalent bonds. Alternatively, one could react the aminegroup on the silicon alkoxide with an anhydride to make an imide for thechemical linkage moiety A.

In addition, nanoparticle precursor structures can be prepared from ahydroxyl containing silicon alkoxide and the reactive reagent having theR group and at least one functional group reactive with the hydroxylgroup on the silicon alkoxide, such as an acids or acyl chlorides toform an ester for the chemical linkage moiety, A in Formula I, capableof forming non-covalent bonds.

Nanoparticles precursor structures can also be prepared from anisocyanate-containing silicon alkoxide and the reactive reagent havingat least one functional group reactive with the isocyanate group, suchas an alcohol and/or an amine to form a urethane and/or a urea for thechemical linkage moiety, A, in Formula I. In one example, a urethane-and/or a urea-containing nanoparticle precursor structure of the formula(Formula I): (R₁O)_(w)Si(R₂-A-R)_(z), where A is the urethane- and/or aurea, are made using an isocyanate-containing silicon alkoxide. Itshould be understood, however, that a variety of polyols and/orpolyamines can be used, including polyester, polyether, andpolycarbonate polyols, for example. Furthermnore, the polyols andpolyamines can be aliphatic (including cycloaliphatic) or aromatic,including heterocyclic compounds, or combinations thereof.

Examples of suitable isocyanate-containing silicon alkoxide compoundsfor preparation of urethane or urea containing nanoparticles precursorstructures of Formula I are typically aliphatic monoisocyantes,diisocyantes and triisocyantes, or combinations thereof. In addition tothe isocyanate groups they can include other functional groups such asbiuret, urea, allophanate, uretidine dione (i.e., isocyanate dimer), andisocyanurate, etc., that are typically used in biomaterials. In oneexample, the isocyanate-containing silicon alkoxide can be3-(triethoxysilyl)propyl isocyanate (Sigma-Aldrich, Milwaukee, Wis.).

Examples of suitable alcohols include anhydrous alcohol such asmethanol, ethanol, propanol, butanol, pentanol, and mixtures thereof.Suitable alcohols have a water content of less than about 1% by weight,especially less than about 0.5% by weight or less than about 0.1% byweight. Other organic solvent(s) (or mixtures of solvents) can also beused that are miscible with the other components.

The present disclosure further provides methods of forming thenanoparticle structure as discussed herein. The nanoparticle structureof Formula III: [(Si—O)_(n)—(Si—O)_(m)]_(p)—(R₂-A-R)_(r) includes thecore of the silicon-oxide based polymer (e.g.,[(Si—O)_(n)—(Si—O)_(m)]_(p)) from which extend the organic group (e.g.,—(R₂-A-R)_(r)) that include the chemical linkage moieties (e.g., “A”)capable of forming non-covalent bonds with portions of the polymer. Inone embodiment, the nanoparticle structure can be formed from thenanoparticle precursor structure of Formula I: (R₁O)_(w)Si(R₂-A-R)_(z)through, for example, a sol-gel process with at least one siliconalkoxide of Formula II: Si(OR³)₄, as discussed herein.

Although certain nanoparticle structures are described herein, thenanoparticle structures of the present disclosure can be formed from awide variety of silicon alkoxides of Formula I and the nanoparticleprecursor structure of Formula II. For example, a method of preparingthe nanoparticle structures involves the combining of (1) thenanoparticle precursor structure of Formula I with (2) at least onesilicon alkoxide of Formula II to form a reaction mixture allowing thenanoparticle structures to form in the reaction mixture.

In one embodiment, the nanoparticle structures can be formed throughsol-gel processes. It has been surprisingly found that sol-gel derivednanoparticle structures impart superior characteristics to compositesused for biomaterials. Moreover, it was surprisingly found that sol-gelderived nanoparticle structures can be incorporated into polymers athigher levels than is conventional possible.

The Sol-gel processes is generally described, for example, in “Sol-GelScience: The Physices and Chemistry of Sol-Gel Processing” (Brinker etal., Academic Press, 1990). As used herein, “sol-gel” refers to anymethod of synthesizing nanoparticle structures that comprises a stepwhere at least one of the precursors is an aqueous or organicdispersion, sol, or solution.

A method for preparing the sol-gel derived nanoparticle structures forthe present disclosure involves the combining of (1) an aqueous ororganic dispersion or sol of the nanoparticle precursor structure ofFormula I: (R₁O)_(w)Si(R₂-A-R)_(z) with (2) an aqueous or organicdispersion, sol, or solution of the desired at least one siliconalkoxide of Formula II: Si(OR₃)₄.

Examples of suitable compounds of Formula I (R₁O)_(w)Si(R₂-A-R)_(z)include 3-(triethoxysilyl)propyl isocyanate, and the like. Examples ofsuitable silicon alkoxide of Formula II: Si(OR₃)₄ includetetraethoxysilane (TEOS), and the like.

The nanoparticle structures can then be used as a bulk material byitself or with one or more additives. The nanoparticle structures canalso be used to form a coating. For example, nanoparticle structures ina solvent can be applied directly to a surface as a coating, where uponsolvent evaporation the coating of the nanoparticle structures isformed. In addition, the nanoparticle structures can also undergoadditional processing techniques to, for example, spin fibers,precipitate particles of the nanoparticle structures and/or form gels ofthe nanoparticle structures. In addition, the nanoparticle structurescan be combined with an appropriate polymer to form the compositematerial of the disclosure. Blends of various silicon alkoxide ofFormula II and/or Formula I are also contemplated.

In one embodiment, the nanoparticle structures are substantiallyunaggregated, where mixtures of these nanoparticle structures are alsocontemplated, as well as combination nanoparticle structures made fromorganic and inorganic materials.

A wide variety of polymers can be used with the present disclosure informing the composite material. Polymers suitable for use in thecomposite material of the present disclosure can include those havingsufficient strength, hydrolytic stability, and non-toxicity to renderthem suitable for use in a biological environment. Polymers of thepresent disclosure in which the nanoparticle structure can be dispersedmay be copolymers, random, alternating, block, star block, segmentedcopolymers (i.e., containing a multiplicity of both hard and softdomains or segments on any polymer chain), or combinations thereof(e.g., where certain portions of the molecule are alternating andcertain portions are random). In addition, polymers of the presentdisclosure can be linear, branched, or crosslinked.

The polymers suitable for forming the composite material according tothe present disclosure further include, but are not limited to, chemicallinkage moieties that have the ability to form non-covalent bonds.Examples of such polymers include those having urethane linkages, esterlinkages, amide linkages, imide linkages, urea linkages, carbonatelinkages, sulfone linkages, ether linkages, and/or phosphonates linkagesfor the chemical linkage moieties, or combinations thereof. Examples ofsuch polymers include polyamide (nylon), polyurethane, polyureas,polyurethane-ureas, and polyester, among others.

In addition, polymers suitable for forming the composite materialaccording to the present disclosure can include both hard and softsegments. As used herein, a “hard” segment is one that is eithercrystalline (i.e., has ordered domains) at use temperature or amorphouswith a glass transition temperature above use temperature (i.e.,glassy), and a “soft” segment is one that is amorphous with a glasstransition temperature below use temperature (i.e., rubbery). Typically,hard segments add considerable strength and higher modulus to thepolymer. Similarly, soft segment adds flexibility and lower modulus, butmay add strength particularly if it undergoes strain crystallization,for example. The polymers can vary from hard and rigid to soft andflexible. In one example, the polymers are elastomers. An “elastomer” isa polymer that is capable of being stretched to approximately twice itsoriginal length and retracting to approximately its original length uponrelease.

Suitable polymers can have a viscosity and molecular weights suitablefor blending and/or melt processing with the nanoparticle structuresdiscussed herein. In addition to the polymers described herein, thecomposite material of the disclosure can also include a variety ofadditives. These can include antioxidants, colorants, processinglubricants, stabilizers, imaging enhancers, fillers, and the like. Thepresent disclosure also provides polymers and compounds used to formsuch polymers, and biomaterials formed from such polymers that can beused in medical devices.

Additional additives can also include, but are not limited to, metalalkoxides M(OR₂)_(n), where the value for n is dependent on theoxidation state of the metal M. In one embodiment, the metal alkoxidescan be incorporated into mixture of the nanoparticle precursor structureand/or the polymer the prior to the sol-gel process. In one embodiment,M can be selected from the group of metals consisting of Groups 2, 4, 5,8, 9, 13, 14 and 15. For example, M can be selected from the group ofmetals consisting of Si, Fe, Ti, Zr, Ir, Ru, Bi, Ba, Al, Ta, and Sr. Inan alternative embodiment, the examples of M can include non-metalelement C and a polyhedral oligomeric silsesquioxane (POSS). Addition ofthe additives such as the metal alkoxide can then be used in the sol-gelprocess to modify the nature of the resulting nanoparticle structureand/or the composite material.

The composite materials of this disclosure include nanoparticlestructures of the present disclosure (e.g., Formula III) dispersed inthe matrix of a polymer. Dispersing the nanoparticle structures into thepolymer can include blending the nanoparticle structures into thepolymer to form a homogeneous mixture, as discussed herein. In oneembodiment, methods of blending the nanoparticle structures into thepolymer can include mixing processes that distribute, incorporate andblend the nanoparticle structures into the polymer. For betterincorporation into the polymer matrix it is advantageous for thenanoparticle structures to include chemical linkage moieties that canform non-covalent bonds, as discussed herein. The use of nanoparticlestructures having chemical linkage moieties that can form non-covalentbonds can enable non-covalent bonding with polymer within a matrix to beachieved. Such non-covalent bonding can allow the core of the siliconoxide based polymer to be incorporated without separating from thepolymer matrix. This miscibility would not other wise be possiblewithout the non-covalent bonding interaction of the chemical linkagemoieties of the nanoparticle structures and the polymer as providedherein.

In an alternative embodiment, the nanoparticle structures of Formula IIIcan be formed from the compounds of Formula I and II, as discussedherein, in situ with the polymer present in the reaction mixture. Forexample, the polymer can be combined with the reactive reagent (e.g., analcohol) and brought into solution under reflux conditions. As usedherein, “solution” does not require complete solubility of the solid butmay allow for some undissolved solid, as long as there is a sufficientamount of the solid dissolved in the reactive reagent for processing.Silicon alkoxides having chemical groups that can form chemical linkagemoieties capable of forming non-covalent bonds can then be added to thereaction mixture under reflux to form the nanoparticle precursorstructure of the Formula I: (R₁O)_(w)Si(R₂-A-R)_(z) in the polymermixture. One or more silicon alkoxides of Formula II can then be addedto form the nanoparticle structures in situ through, for example,sol-gel processes, as discussed herein.

Methods of preparing the nanoparticle precursor structures, thenanoparticles, and the composite materials that include the nanoparticlestructures in the polymer are also provided. In a typical reaction, thecompound(s) of Formula I, as described herein, and the at least onesilicon alkoxide compound of Formula II are combined in a cross-linkingprocess to form the nanoparticle structure of Formula III. An example ofsuch a cross-linking process includes the sol-gel process

Three reactions are generally used to describe the sol-gel process:hydrolysis, alcohol condensation, and water condensation. Thecharacteristics and properties of the nanoparticle structure of FormulaIII formed through the sol-gel process can be related to a number offactors that affect the rate of hydrolysis and condensation reactions,such as, pH, temperature and time of reaction, reagent concentrations,catalyst nature and concentration, aging temperature and time, anddrying. Controlling these factors allow for the structure and propertiesof the sol-gel-derived nanoparticle structure of Formula III to bevaried as desired.

A method for preparing the nanoparticle structure for the presentdisclosure through a sol-gel process involves the combining of (1) themixture of the compound(s) of Formula I and the least one siliconalkoxide of Formula II and (2) an aqueous or organic dispersion or solof reagents that include at least one alcohol and a catalyst providedunder conditions for the sol-gel reaction to take place.

Examples of suitable catalysts include mineral acids such ashydrochloric acid (HCl), ammonia, acetic acid, potassium hydroxide(KOH), titanium alkoxides, vandium alkoxides, amines, KF, and HF.Additionally, it has been observed that the rate and extent of thehydrolysis reaction is most influenced by the strength and concentrationof the acid- or base-catalyst. In one embodiment, the concentration ofthe acid- or base-catalyst can be from 0.01 M to 7M. In addition, thenature of the nanoparticle structure can be influenced by the selectionof an acid or base catalyst, where under acid-catalyzed conditions thenanoparticle structure yields primarily linear or randomly branchedpolymers which entangle and form the nanoparticle structure. On theother hand, nanoparticle structures derived under base-catalyzedconditions can yield more highly branched clusters which do notinterpenetrate prior to gelation and thus behave as discrete clusters.

Examples of suitable alcohols include anhydrous alcohol such asmethanol, ethanol, propanol, butanol, pentanol, and mixtures thereof.Suitable alcohols have a water content of less than about 1% by weight,especially less than about 0.5% by weight or less than about 0.1% byweight. Other organic solvent (or mixtures of solvents) can also be usedthat are miscible with the other components.

According to the present disclosure, the sol-gel reaction can take placewith the reagents in either a liquid phase and/or a gas phase. Typicalreaction conditions for the sol-gel reaction can occur in a temperaturerange of 20° C. to 100° C. Other temperature ranges are also possible.

Such methods are exemplary only. The present disclosure is not limitedby the methods described herein for making the compounds of Formula IIIor the composite materials derived from the compounds of Formula III.

The invention has been described with reference to various specific andpreferred embodiments. It is understood, however, that there are manyextensions, variations, and modification on the basic theme of thepresent invention beyond that shown in the detailed description, whichare within the spirit and scope of the present invention.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this disclosure will become apparent tothose skilled in the art without departing from the scope and spirit ofthis disclosure. It should be understood that this disclosure is notintended to be unduly limited by the illustrative embodiments set forthherein and that such embodiments are presented by way of example onlywith the scope of the disclosure intended to be limited only by theclaims set forth herein as follows.

1. A nanoparticle structure comprising a compound of the formula[(Si—O)_(n)—(Si—O)_(m)]—(R₂-A-R)_(r); where A is a chemical linkagemoiety that can form a non-covalent bond with a polymer, R and R₂ areeach independently an organic group; n, m and p are each independentlyin a polymeric range; r is at least 25 percent of n.
 2. The nanoparticlestructure of claim 1, where the nanoparticle structure is derived from ananoparticle precursor structure of the formula (R₁O)_(w)Si(R₂-A-R)_(z)and at least one silicon alkoxide of the formula Si(OR₃)₄ in a sol-gelprocess, where A is the chemical linkage moiety that can form anon-covalent bond with the polymer, R, R₁, R₂ and R₃ are eachindependently an organic group, and w and z are each independently 1 to3.
 3. The nanoparticle structure of claim 2, where[(Si—O)_(n)—(Si—O)_(m)]_(p) is a silicon oxide based polymer that formsa nanoparticle from which the groups (R₂-A-R)_(r) extend.
 4. Thenanoparticle structure of claim 3, where the silicon oxide based polymerof the nanoparticle is formed using the sol-gel process.
 5. Thenanoparticle structure of claim 2, where A is a urethane group.
 6. Thenanoparticle of claim 2, where R is a (C1-C8)alkyl group and R₂ is a(C1-C18)alkylene group.